OE
One good clue to the first blank is the word “loyalist.” Those fighting the loyalists would likely be the rebels. You don’t have any indication that the forces were fascistic (totalitarian, led by dictator). Outclassed (surpassed in quality) is irrelevant here, so revolting fits best. Don’t be thrown off by the dual meaning of revolting—certainly revolting can mean “disgusting,” but it can also mean engaging in a revolt, such as against a government. The loyalist battalion was helped or strengthened by “its allies’ reinforcements,” so only bolstered (supported) makes sense. Obviated (anticipated and made unnecessary) isn’t supported by any proof in the sentence. Sapped (weakened, especially of energy) conflicts with the idea that allies would help the loyalists.